The present invention relates to aspects of control of a chemical laser.
A chemical laser can be defined generally as a device in which a negative temperature and population inversion can be obtained as a result of one or several chemical reactions, with or without additional collision among the different molecules and/or atoms of a gas, but under particular pressure and/or temperature conditions permitting emission of radiation of one or several particular frequencies by stimulation through photons of like frequency or frequencies. This laser action, of course, occurs within a particular gas zone or region which gas is kept moving at a rather high speed, for purposes of replenishing the particular components actively participating in the laser action. Therefore, the laser cavity, as an optical cavity, is continuously traversed by a flow of various fluids which include the laser active component or components.
The laser beam traverses that flow region, and the particular beam or better, any particular ray of the beam as it traverses that flow region, will in parts be absorbed, attenuated, scattered, etc., by the gas flow, while stimulating action augments the intensity of the particular ray. As a consequence, each ray as it traverses this laser and gas flow cavity will, in total, either increase or decrease in intensity, i.e., will exhibit a positive or a negative gain (or a gain larger or smaller than unity depending on the definition of gain). At any given time and for an assumed state under stable fluid flow conditions, one can, therefore, define a gain profile across the flow region; more precisely, a gain profile can be defined along the flow region but across the laser cavity because usually the flow path extends transversely to the optical path in the cavity. Variations in fluid supply, fluid pressure, combustions or other reactions, and temperatures, also, possibly variations in nozzle dimensions, etc., are all parameters which may vary the gain as a whole, as well as the profile of the gain across the laser cavity. Variations of these parameters involve particularly the location of that portion of the gain curve which has positive values. As a consequence, the total power output of the laser as well as its intensity profile will vary greatly. This gain variation poses a problem which has to be resolved.